Historically, steel pipe or black iron pipe was the most common choice for transporting water and flammable gases from one location to another, such as from a supplier to a consumer such as at a home. In the context of flammable gases, black pipe was used in this manner due to its robustness, including a high resistance to heat and high pressure. Straight runs of black pipe may be joined using threaded connection ends. Additionally, various threaded connectors may be used to route the black pipe around obstacles or to change its direction. Alternatively or in addition to threading, the pipe sections and connections may also be joined to the fittings through welding. This provides a very sturdy line through which fuel may flow. However, routing black pipe is often very time consuming and very labor intensive due to the weight of the pipe and the need to weld each of the pieces.
In recent years, an alternative to black pipe has been offered—corrugated stainless steel tubing (CSST). CSST consists of a thin, continuous, flexible stainless steel pipe that may transport and distribute natural gas. In comparison to traditional black pipe, CSST is lighter in weight and requires fewer welded and threaded connections due to its flexibility. However, one significant disadvantage in the use of this form of tubing is its propensity to failure. CSST tends to have narrow sidewall thicknesses (e.g., ˜10 millimeters). Narrow walls allow the tubing to remain flexible and easy to maneuver. However, the thin walls also make the tubing prone to puncture or other failure when exposed to rough handling, sharp objects, shock, etc. Once punctured, the tubing may leak fuel, which may be ignited through nearby open flames, sparks, electrical current, self ignition, etc.
This problem is prevalent in the heating and air conditioning industry, which makes extensive use of CSST. In residential applications, CSST is often connected to the fuel source at or near the gas meter and then runs to one or more appliances that rely on gas fuels (e.g., gas heater, gas dryer, gas stove, fireplace, etc.). During a lightning storm or a thunderstorm, the tubing may be energized with electrical energy from lightning strikes at or near the residence. Once energized, electrical arcing may occur between the tubing and nearby objects that are grounded. When this happens, holes may be created in the CSST due the large current associated with electrical strikes. These holes may vary is size from very small, such as a pinhole, to very large, such as 2 or more inches in diameter. In addition to creating these holes, the electrical arcing may also ignite the fuel that escapes from the tubing. As fuel continues to be supplied to the tubing, it continues to burn within the structure and often ignites the structure.
Therefore, what is needed is an automatic fuel shutoff valve for use with a fuel line that responds to the presence of electrical current in the fuel line and interrupts the flow of fuel through the fuel line.